linux-kernel - Re: [PATCH v2 1/3] dt-bindings: media: ov772x: Document endpoint properties

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Message-ID: <CA+V-a8tk_KNoie0=aLBnj31RYoeHqHp8jnxqyJcPxWbkq6xTRA@mail.gmail.com>
Date:   Mon, 10 Aug 2020 08:22:52 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Jacopo Mondi <jacopo@...ndi.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media <linux-media@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: media: ov772x: Document endpoint properties

Hi Jacopo,

Thank you for the review.

On Thu, Aug 6, 2020 at 3:32 PM Jacopo Mondi <jacopo@...ndi.org> wrote:
>
> Hi Prabhakar,
>
> On Mon, Aug 03, 2020 at 12:39:11PM +0100, Lad Prabhakar wrote:
> > Document endpoint properties required for parallel interface
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > ---
> >  .../devicetree/bindings/media/i2c/ov772x.txt     | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/media/i2c/ov772x.txt b/Documentation/devicetree/bindings/media/i2c/ov772x.txt
> > index 0b3ede5b8e6a..1f4153484717 100644
> > --- a/Documentation/devicetree/bindings/media/i2c/ov772x.txt
> > +++ b/Documentation/devicetree/bindings/media/i2c/ov772x.txt
> > @@ -21,6 +21,22 @@ subnode for its digital output video port, in accordance with the video
> >  interface bindings defined in Documentation/devicetree/bindings/media/
> >  video-interfaces.txt.
> >
> > +Endpoint node required properties for parallel connection are:
> > +- remote-endpoint: a phandle to the bus receiver's endpoint node.
>
> we allow endpoints without a remote end connected usually. They can be
> filled in later, in example, with an overlay.
>
Agreed.

> > +- bus-width: shall be set to <8> for 8 bits parallel bus
> > +          or <10> for 10 bits parallel bus
> > +- data-shift: shall be set to <2> for 8 bits parallel bus
> > +           (lines 9:2 are used) or <0> for 10 bits parallel bus
>
> defining what is required or optional might be hard. I don't see the
> driver enforcing their presence and I assume they have safe default.
> Maybe make them optional and specify what the defaul value is ?
>
Will do.

>
> > +- hsync-active: active state of the HSYNC signal, 0/1 for LOW/HIGH respectively.
> > +             (Not required for bus-type equal 6)
> > +- vsync-active: active state of the VSYNC signal, 0/1 for LOW/HIGH respectively.
> > +             (Not required for bus-type equal 6)
>
> If they're not required, they're optional, aren't they ? :)
>
Agreed.

> > +- pclk-sample: sample data on rising (1) or falling (0) edge of the pixel clock
> > +            signal. (Not required for bus-type equal 6)
>
> Why the pclk polarity is does not apply to BT.656 ?
>
No it should apply.

> > +- bus-type: data bus type. Possible values are:
> > +         5 - Parallel
> > +         6 - Bt.656
>
> Are we making this required, or do we expect this to be deduced
> depending on which other properties have been specified ? Sakari it
> seems you would like this to become a properties that has to be
> specified most of the times, right ? (I tend to agree with that FWIW),
> but does it impact retro-compatibility ?
>
Agreed can be deduced from other properties. But shall wait for Sakari
to comment.

Cheers,
Prabhakar

> > +
> >  Example:
> >
> >  &i2c0 {
> > --
> > 2.17.1
> >